A transformer rated 10 MVA, 33/11 kV has a per-unit impedance of $0.05\,\text{pu}$ on its own base. On a new system base of 100 MVA and 33 kV (HV side), the per-unit impedance becomes:

Home › MCQs › Electrical Engineering › Question #2159

Electrical Engineering QUESTION #2159

Question 1

$0.5\,\text{pu}$✔️
$0.005\,\text{pu}$
$0.05\,\text{pu}$
$5\,\text{pu}$

Correct Answer Explanation

$Z_{pu,new} = Z_{pu,old} \times \frac{MVA_{base,new}}{MVA_{base,old}} \times \left(\frac{kV_{base,old}}{kV_{base,new}}\right)^2 = 0.05 \times \frac{100}{10} \times 1 = 0.5\,\text{pu}$.

More Options